Dementia Rate in Parkinson's Shifts With Age

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Dementia with Lewy bodies is a neurodegenerative disorder characterized by parkinsonism and cognitive dementia which develops before, or within 1 year after, parkinsonism onset. The term Parkinson's disease dementia is used when dementia appears more than 1 year after the onset of otherwise typical Parkinson's disease.

The overall incidence rate of dementia with Lewy bodies is lower than the rate of Parkinson's disease and the incidence increases steeply with age and is markedly higher in men.

Dementia with Lewy bodies (DLB) occurred infrequently in patients with parkinsonism, but the rate increased steeply with age, according to data from a 15-year period.

DLB occurred in 64 of 542 patients with newly diagnosed parkinsonism from 1991 to 2005, and 46 patients developed Parkinson's disease dementia (PDD), resulting in an overall dementia rate of 5.9 per 100,000 person-years.

DLB was associated with an earlier onset and more hallucinations and cognitive fluctuations as compared with PDD, and men predominated across the age spectrum, Walter A. Rocca, MD, of the Mayo Clinic in Rochester, Minn., and colleagues reported online in JAMA Neurology.

"Our study provides unique population-based data on the incidence of DLB and PDD in Olmsted County," the authors concluded. "Similar to Parkinson's disease, the risk of DLB increases with older age and is more frequent in men.

"Interestingly, the men-versus-women incidence rate ratio is greater for DLB than for Parkinson's disease and may suggest different etiologic mechanisms for DLB in men versus women."

First described several decades ago, DLB remains a diagnostic challenge because of its overlap with other neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and frontotemporal lobar degeneration. DLB is distinguished from PDD primarily by earlier onset, defined as with 1 year after onset of Parkinson's disease.

Little is known about the epidemiology of DLB or PDD in the general population. To address the issue, investigators examined records of the well-defined population of Olmsted County, Minn., which includes Rochester. They identified all patients who developed Parkinson's disease, DLB, and PDD over a 15-year period.

With respect to DLB, men had a rate more than twice that of women (4.8 versus 2.2 per 100,000 person-years). In patients ≥65, the overall rates were 54.2 per 100,000 person-years in men and 16.2 per 100,000 person-years in women.

The first DLB diagnoses occurred in patients ages 60 to 69, and the rate in men increased from 12.7 per 100,000 person-years to 77.8 per 100,000 person-years during ages 70 to 79, and remained at 55.7 per 100,000 person-years among men 80 to 99.

Among women, the rate was 8.2 per 100,000 person-years during ages 60 to 69, increased to 19.5 per 100,000 person-years in the next decade, and then declined to 18.9 per 100,000 person-years for ages 80 to 99.

PDD had a similar distribution in men (2.3 per 100,000 person-years) and women (2.7 per 100,000 person-years), and the rate among patients ≥65 was 23.8 per 100,000 person-years in men and 22.5 per 100,000 person-years in women.

For DLB and PDD combined, men had an overall rate of 78.0 per 100,000 person-years as compared with 38.7 per 100,000 person-years for women. Rates were similar during ages 60 to 69 (14.5 per 100,000 person-years for men, 13.1 per 100,000 person-years for women) but increased more rapidly with age in men.

Among men ages 70 to 79, the rate of DLB and PDD combined was 98.0 per 100,00 person-years, increasing to 123.8 per 100,000 person-years during ages 80 to 99. Corresponding rates for women were 39.0 and 56.8 per 100,000 person-years. The overall rate of the two conditions was 7.1 per 100,000 person-years in men and 4.9 per 100,000 person-years in women.

The study had some limitations such as potentially missing data on patients with mild symptoms and some clinical features going unrecognized because they were not in the medical records. Also, Olmsted County is a predominantly white community so the findings may not be generalizable.

"There is a paucity of published incidence data relating to DLB despite the fact that DLB is presumed to be the second leading cause of neurodegenerative dementia after Alzheimer disease," the authors said of their findings. "The overall incidence rate of DLB in our population-based study was 3.5 cases per 100,000 person-years.

"To put this into context, Parkinson's disease incidence was four-fold higher, with an incidence rate of 14.2 cases per 100,000 person-years. In fact, the overall incidence of Parkinson's disease in our county was 2.4 times higher than the incidence of DLB and PDD combined (14.2 versus 5.9)."

The study was supported by the National Institute on Aging.

The authors reported no conflicts of interest.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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